I recently bought a used Powermatic 50 jointer. All three knives were shot. After reading online, I tried to sharpen the knives in place – no luck. So I built a small sharpening jig that I found on LJ’s. The jig is sweet, and would work really well, but the last owner, (maybe the owner before that) tried to regrind two of the knives and ruined them.

I ordered a new set – no big deal.

After reading the zillion and a half articles online about setting and replacing jointer knives I’m a little intimidated on the process. This is definitely a case of information overload. Some say they need to be exactly the same height as the outfeed table. Some recommend a few thousands proud of the outfeed table. Some reference the distance between the bevel and the cutter head. All agree that precision is absolutely critical to a functioning machine.

Here’s how I understand/plan to approach it:

1. I set the infeed table to the zero position – and made sure I got any sag out using a nice straight edge. I now have less then .0015 clearance at any point on the straight edge across the length of the tables – per the manufacturer’s instructions

2. Find top dead center on the cutter head using a dial indicator on a magnetic stand. The Garage Woodworks guy (thanks!) has a video showing this. According the video I put the magnetic base on the infeed table and locate top dead center on the portion of the cutter head that does not have a knife slot. Top dead center is the highest point in the arc of the cutter head.

3. Mark Top Dead Center on the fence as a reference point.

Here’s where I get fuzzy on the process.

4. Insert new blade so that it rests on the jack screws and tighten the gib screws very lightly.

5. Place the magnetic blade lifters (small jigs I made using magnets and pieces of flat steel) on the outfeed table. Position the cutter head so the blade is on the Top Dead Center mark on the fence and move the magnetic jig to the blade so that it lifts it up, even with the outfeed table.

6. Tighten down gib screws.

Move on to the next one.

So, my question for the wise masses on LJ’s: Does this sound like a reasonable process? Is it accurate enough? Am I missing something? Is there something that would simplify the process?

Thanks in advance folks!

-- Steve

11 replies so far

I don’t see anything about locking down the knives.Other that that I did it pretty much the same way last week.After I lock the knives I back the jack screws out against the knife bottom just for good measure.I then zero my dial indicator on the outfeed table and check the knife with it to make sure it’s close to zero about .001” or less.

Thanks for the quick response cutworm, and the confirmation that the process is right.

that’s a good suggestion, thank you.

It feels like a really simple procedure, so maybe I am just making a mountain out of mole hill in my head. After reading/watching all the videos and seeing posts that describe it as difficult and tedious and whatever else, I was assuming that it was a miserable process.

There is a more low tech way of doing it for anyone without a dial indicatorInfeed table is wound up to same height as outfeed, then a small flat stick with two pencil marks 1/8 apart is placed over the cutter block with the front mark level with edge of the outfeed table. Turn the cutter block so the knife catches the stick and lifts it onto the infeed table. Adjust the height of the knife until the stick only travels between the front mark and the back mark. Do this at each edge and the middle of each knife.

I basically used Renners’ method but used a steel rule instead of the “small flat stick”. The most tedious part of mine was getting the knives all level across the width of the table. I think those magnetic jigs address this problem.

1+ Renners method for those that don’t own a dial indicator. As long as the blades are flush with the outfeed table, you should get good results. The part about tightening the blade screws gradually is important so the blade setting doesn’t shift. Remember, it feels like you are loosening the blade bolts to tighten them. People make it sound like a difficult procedure, but with a little patients and the right tools it becomes a simple task.

-- Willie, Washington "If You Choose Not To Decide, You Still Have Made a Choice" - Rush

It’s all done. It took about 1 hour total – which isn’t bad IMO. I was expecting 2+ for my first try. It was a fairly painless procedure overall.

Just like Pinto said – as long as you have patience it wasn’t bad at all.

I pretty much followed the procedure I listed above. I had to fiddle with the knives/jack screws a little bit. But using the dial indicator on the base, and the jack screws for micro adjusting, it was pretty easy to get it set to wherever I wanted it.

The magnetic jigs were a life saver. I think it would have been a tremendous pain to do it without them. They held the blade where I wanted it, and locked the cutter head, but still allowed me to wiggle it back and forth enough to make sure I was top dead center.

The first cuts with fresh blades were AWESOME! I can’t believe I’ve gone this long without one of these things.